The present invention relates to an ink jet recording head for effecting image or the like printing by ejecting ink onto a recording material, a manufacturing method for the same, an ink jet recording apparatus and a driving method for an ink jet recording head. More particularly, it relates to an ink jet recording head in which a proper amount of energy is supplied to a recording element for generating energy contributable to ink ejection, a manufacturing method of the same, an ink jet recording apparatus using the same and actuating or driving method for the same.
A recording apparatus such as a printer, a copying machine, a facsimile machine or the like, or a recording apparatus as outputting equipment of a work station or a combined system including a computer, word processor or the like, effects recording of an image or the like on a recording sheet such as a sheet of paper, plastic thin plate (OHP for example) in accordance with image information. The recording apparatus is classified, depending on the recording method using recording means, into an ink jet type, a wire dot type, a thermosensitive type, a thermal transfer type, a laser beam type or the like.
Among them, the ink jet type recording device (ink jet recording apparatus) uses a recording means (recording head) from which the ink is ejected onto the recording sheet. This type is advantageous in that the size of the recording means is small, that high-speed printing with high resolution is possible, that plain paper is usable without special treatment thereto, that running cost is low, that noise is low (non-impact type), and color image printing is easy using a plurality of colors of ink.
The ink jet recording type is further classified into various types, in one of which a heat generating element is provided in a nozzle and is actuated to produce heat which is used to eject the ink (bubble jet recording system). The recording element for generating the energy to eject the ink can be manufactured through a semiconductor manufacturing process. Therefore, the recording head or the Bubble Jet type comprises an element substrate made of silicon substrate, a recording element formed thereon and a top plate of resin material such as polysulfone or glass or the like having grooves therein which constitute ink passages.
In some of the recording heads of this type, drivers for driving the recording elements, temperature sensors for controlling the recording elements in accordance with head temperatures and a drive control portion or the like are formed on the element substrate as well utilizing the material (silicon substrate) of the element substrate.
FIG. 9 shows an example of a substrate for the recording head.
In FIG. 9, formed in the element substrate 900 are a plurality of juxtaposed heat generating elements (recording elements) 901 for applying thermal energy for ink ejection, a power transistor (driver) 902 for driving the heat generating elements 901, a shift register 904 for receiving serial image data supplied from an external device, a serial clock in synchronism therewith to receive the image data of 1 line at a time, a latching circuit 903 for latching the image data of one line outputted from the shift register 904 in synchronism with the latching clock signals and for parallel transfer thereof to the power transistor 902, a plurality of AND gates 915, provided corresponding to each of the power transistors 902, for applying output signals of the latching circuit 903 to the power transistor 902 in accordance with external enabling signals 908, and input contacts 905-912 for inputting the image data and various signals from the outside.
On the element substrate 900, there are formed a temperature sensor reference numeral 914 for measuring a temperature of the element substrate 900 and a heater for heating the element substrate on the basis of the temperature detection of the element substrate 900 by the temperature sensor. U.S. Pat. No. 5,175,565, for example, discloses an element substrate in which the temperature sensor and the heater are built-in at the opposite outside portions of a recording element array. With this structure, the problem of such a temperature distribution of the element substrate 900 as will lead to unstable ink ejection can be avoided. That is, the temperature distribution is detected by the temperature sensor, and in response to the detection, the heater is actuated to correct the temperature distribution of the temperature. Thus, stabilized ink ejection is accomplished. A recording head having on the element substrate the driver, the temperature sensor, the drive control portion and so on, has been put into practice, and is advantageous in the reliability and the downsizing of the apparatus.
With this structure, the image data inputted as the serial signal are converted to the parallel signals by the shift register 904, and are outputted and retained by the latching circuit 903 in synchronism with the latching clock signals. In such state, when a driving pulse signal for the heat generating element 901 (enabling signal 908 for the AND gate 915) is inputted through the input contact 908, the power transistor 902 is actuated in accordance with the image data to supply the electric current to the corresponding heat generating element 901, thus heating the ink in the liquid flow path (nozzle), by which the ink is ejected in the form of a droplet through the nozzle.
However, the ink jet recording heads include differences among individuals due to the tolerances during the manufacturing step, and therefore, the driving voltage applied to a recording element may be higher than a driving voltage supplying a proper amount of energy with a result of shorter service life than expected, or conversely, the driving voltage applied to the recording element is smaller than the driving voltage supplying the proper amount of energy with a result of ejection defect.
U.S. Pat. No. 5,943,069 proposes using the temperature control heater as a resistance sensor, and the resistance of the heater is detected, and on the basis of the detected resistance, a proper driving voltage to be applied to the heat generating element 901 is selected. U.S. Pat. No. 5,943,069 also discloses that in consideration of the possibility that when the size of the substrate (element substrate) is large, because of variations of the resistance values of the heat generating elements (recording elements), a resistance sensor is built-in at each of opposite outside portions of the recording element array. The resistances of the resistance sensors are sequentially detected, and on the basis of the output, the driving voltage to be applied to the recording element is selected.
Recently, the number of nozzles of a recording head has increased in order to raise the recording speed, to such an extent that the length of the array of the nozzles (recording width) is 100 mm, or 200 mm (full-line type). However, in the development of long recording heads, it has turned out that the above-mentioned problems arise again when the recording width is increased. More particularly, even if the resistance sensors as disclosed in said U.S. Pat. No. 5,943,069 are used, some of the recording elements have shorter service lives, or some other recording elements have ejection defects.
The inventors first thought that problems could be solved by special use of the resistances of the two resistance sensors, although U.S. Pat. No. 5,943,069 did not disclose how to use the resistances sequentially detected by the two resistance sensors.
The inventors have noted the possibility that variations in the resistances of the recording elements are greater when the size of the substrate is large as pointed out by U.S. Pat. No. 5,943,069, and the inventors experiments and considerations have revealed that if the variations relative to a sheet resistance value is approx. 4%, the problems of the short service life and ejection defect do not arise, and the recording heads are practically operable.
Description will be made as to the nature of the variations in the resistances of the recording elements, which arise during the manufacturing step.
In order to produce a heat generating element on the substrate for the ink jet recording head, particularly one which ejects the ink by the generation of a bubble using a heat generating element (recording element), a heat generation layer is formed on a wafer having a diameter of 125 mm (5 inches) or 150 mm (6 inches) or the like, and the heat generation layer is patterned into a proper shape.
FIG. 10 is a graph showing a change of a sheet resistance (broken line) in a cross-section Axe2x80x94A on the wafer having the heat generation layer on its surface. The variation is created mainly by variations in the film thickness when the film is formed, or variations in the composition or the like in the wafer surface. The difference between the maximum resistance and the minimum resistance is approx. 10-15%. Referring to FIG. 10, the characteristics of the variation (broken line) of the sheet resistance will be described. In the circumference portion of the wafer 2001 indicated by hatched lines, the difference is large. This is because the film formation speed and/or the film formation condition tend to vary more in the circumference portion than in the central portion of the wafer during the film formation.
Referring to FIG. 11, the cutting out of the substrate having a recording width of a conventional size (10 mm) from the wafer will be described. FIG. 12 schematically shows the case in which a larger size substrate (20 mm) is cut out. These Figures show a concept of variations in the resistances of the recording elements in substrates having different sizes (recording widths).
In the conventional structure, the electric energization time (period) has been determined on the basis of the value detected by a measurement element at one point. Therefore, the recording elements away from the resistance sensor are supplied with excessively large or small energy, and excessiveness increases with the distance from the resistance sensor. Therefore, the reduction of the service life and the ejection failure occur more frequently in the more distant recording elements.
FIG. 13 shows variations (%) in the resistances of the recording elements relative to the resistance value of the measurement resistance in the conventional size (10 mm) (recording width) substrate and a large size (20 mm) substrate, which have been cut out of a central portion of the wafer in which the variations in the sheet resistance of the heat generating element is relatively small. As shown in FIG. 13, the variation in the conventional size substrate is approx. 1%, and the variation in the large size substrate is approx. 3%; therefore, the variations are not larger than 4%. Therefore, in the center portion region of the wafer, the influence of the sizes are not serious, and therefore, the produced substrates are satisfactory.
FIG. 14 shows variations (%) in the resistance values of the recording element relative to the measurement resistance, as to the conventional size (10 mm) substrate and the large size (20 mm) substrate, which have been cut out of the peripheral portion of the wafer in which the variations in the sheet resistance of the heat generating element are relatively large. As shown in FIG. 14, the variations in the conventional size substrate are approx. 4% at the maximum, and therefore are satisfactory. However, the large size substrate exhibits approx. 8% variations, which means that there are probabilities of shorter service life or ejection failure. This is a cause of reduction of the yield in the substrate manufacturing.
Accordingly, it is a principal object of the present invention to provide an ink jet recording head, an ink jet recording head manufacturing method, an ink jet recording apparatus and a driving method for an ink jet recording head wherein even if the recording width is relatively large, and therefore, the variations in the resistances of the recording elements are relatively large, the yield of the substrates is not degraded, and the service life can be maintained, and the ejection defect can be avoided.
According to an aspect of the present invention, there is provided an ink jet recording head comprising:
a plurality of recording elements arranged in an array on a substrate, said recording elements having electric resistances with a variance not less than 4% from a resistance value of at least one of said recording elements, wherein the recording elements generate ink ejection energy to effect printing;
a plurality of measuring elements, disposed adjacent at least each of the opposite ends of the array of said recording elements, for detecting characteristic values of said recording elements; and
storing means for storing an average, a median or a reference value corresponding thereto.
According to this aspect of the present invention, the variations of the resistances of the recording elements relative to the reference value can be made approx. one half the conventional variations. Therefore, even if the size of the substrate is relatively large, the variations can be reduced, and therefore the problems of short service life and the ejection defect can be avoided.
It may be that the characteristic values are resistances of said measuring elements.
It may be that said recording elements comprise heat generating elements.
It may be that the array of the recording elements has a length not less than 20 mm.
It may be that an additional measuring element is disposed between said measuring elements disposed adjacent to the ends of the array of the recording elements.
It may be that measuring element contacts are connected to opposite ends of each of the measuring elements.
It may be that a measuring element contact is connected to one end of each of the measuring electrodes disposed adjacent the opposite ends of the array of the recording elements.
It may be that the resistance of the wiring is not more than {fraction (1/10)} a total of the resistances of the measuring electrodes.
It may be that said array of the recording elements is divided into a plurality of groups of said recording elements, and said plurality of measuring elements for detecting characteristic values of said recording elements are disposed at least at the opposite ends of the respective groups of the recording elements.
It may be that at least one recording element driving signal contact is connected to each of the groups of said recording elements to supply driving signals for generating the ejection energy to said recording elements therein with the same pulse width to cause said recording elements to generate ink ejection energy.
It may be that the groups of the recording elements have a length not less than 20 mm.
According to another aspect of the present invention, there is provided an ink jet recording head comprising:
a plurality of recording elements arranged in an array on a substrate, said recording elements having electric resistances with a variance not less than 4% from a resistance value of at least one of said recording elements, wherein the recording elements generate ink ejection energy to effect printing;
a plurality of measuring elements, disposed adjacent at least each of the opposite ends of the array of said recording elements, for detecting characteristic values of said recording elements;
wherein outputs of said measuring elements are used to determine amounts of electric energy of driving signals to be supplied to said recording elements to generate the ejection energy.
According to this aspect of the present invention, even if the size of the substrate is relatively large, the influence of the variations of the resistances of the recording elements can be reduced. Thus, a larger size of the substrate is usable.
It may be that an average, a median or a reference value corresponding thereto of the characteristic values is used for determining the amounts of the electric energy.
It may be that the characteristic values are resistances of said measuring elements.
It may be that said recording elements comprises heat generating elements.
It may be that the array of the recording elements has a length not less than 20 mm.
It may be that an additional measuring element is disposed between said measuring elements disposed adjacent to the ends of the array of the recording elements.
It may be that measuring element contacts are connected to opposite ends of each of the measuring elements.
It may be that a measuring element contact is connected to one end of each of the measuring electrodes disposed adjacent the opposite ends of the array of the recording elements.
It may be that the resistance of the wiring is not more than {fraction (1/10)} a total of the resistances of the measuring electrodes.
It may be that said array of the recording elements is divided into a plurality of groups of said recording elements, and said plurality of measuring elements for detecting characteristic values of said recording elements are disposed at least at the opposite ends of the respective groups of the recording elements.
It may be that at least one recording element driving signal contact is connected to each of the groups of said recording elements to supply driving signals for generating the ejection energy to said recording elements therein with the same pulse width to cause said recording elements to generate ink ejection energy.
It may be that the amounts of the electric energy of the driving signals to be supplied to said recording elements are capable of being controlled for respective groups.
It may be that the amounts of the electric energy of the driving signals to be supplied to said recording elements are the same within the respective groups.
It may be that the ink jet recording head further comprises storing means for storing an average, a median or a reference value corresponding thereto.
It may be that the characteristic values are resistances of said measuring elements.
It may be that said recording elements comprise heat generating elements.
It may be that the groups of the recording elements have a length not less than 20 mm.
It may be that an additional measuring element is disposed between said measuring elements disposed adjacent to the ends of the array of the recording elements.
It may be that measuring element contacts are connected to opposite ends of each of the measuring elements.
It may be that a measuring element contact is connected to one end of each of the measuring electrodes disposed adjacent the opposite ends of the array of the recording elements.
It may be that the resistance of the wiring is not more than {fraction (1/10)} a total of the resistances of the measuring electrodes.
According to a further aspect of the present invention, there is provided a manufacturing method for an ink jet recording head including a substrate having a plurality of recording elements arranged in an array on a substrate and a plurality of measuring elements, disposed adjacent at least each of the opposite ends of the array of said recording elements, for detecting characteristic values of said recording elements; and storing means for storing an average, a median or a reference value corresponding thereto, wherein the recording elements generate ink ejection energy to effect printing, said method comprising:
a step of detecting the characteristic values;
a step of calculating an average, a median or a reference value corresponding thereto from the characteristic values;
a step of storing in the storing means the average, the median or the reference value.
According to the manufacturing method for the ink jet recording head according to this aspect of the present invention, the ink jet recording head with suppressed variations of the resistances of the recording elements can be manufactured. In addition, it is not necessary to select the substrates depending on the variations of the resistances of the recording elements, and therefore, the manufacturing cost can be reduced.
It may be that a variance of electric resistances of the recording elements is not less than 4% from resistance value of at least one of said recording elements.
It may be that the characteristic values are resistances of the measuring elements.
It may be that the recording elements and the measuring elements are produced in the same process step.
It may be that the array of the recording elements has a length not less than 20 mm.
It may be that an additional measuring element is disposed between said measuring elements disposed adjacent to the ends of the array of the recording elements.
It may be that measuring element contacts are connected to opposite ends of each of the measuring elements.
It may be that a measuring element contact is connected to one end of each of the measuring electrodes disposed adjacent the opposite ends of the array of the recording elements.
It may be that the resistance of the wiring is not more than {fraction (1/10)} a total of the resistances of the measuring electrodes.
It may be that said array of the recording elements is divided into a plurality of groups of said recording elements, and said plurality of measuring elements for detecting characteristic values of said recording elements are disposed at least at the opposite ends of the respective groups of the recording elements.
It may be that at least one recording element driving signal contact is connected to each of the groups of said recording elements to supply driving signals for generating the ejection energy to said recording elements therein with the same pulse width to cause said recording elements to generate ink ejection energy.
It may be that the groups of the recording elements have a length not less than 20 mm.
According to a further aspect of the present invention, there is provided an ink jet recording apparatus comprising:
an ink jet recording head including a plurality of recording elements arranged in an array on a substrate, said recording elements having electric resistances with a variance not less than 4% from a resistance value of at least one of said recording elements, wherein the recording elements generate ink ejection energy to effect printing; a plurality of measuring elements for detecting characteristic values of said recording elements;
characteristic value detecting means for detecting characteristic values of said measuring elements;
calculating means for obtaining an average, a median or a reference value corresponding thereto from the characteristic value; and
driving signal supply means for determining amounts of electric energy of driving signals to be supplied to said recording elements to generate the ejection energy on the basis of the average, the median or the reference value corresponding thereto and for supplying in the driving signals to said recording elements.
It may be that said characteristic values are resistances of the measuring electrodes.
It may be that said apparatus further comprises storing means for storing the average, the median or the reference value.
It may be that said array of the recording elements is divided into a plurality of groups of said recording elements, and said plurality of measuring elements for detecting characteristic values of said recording elements are disposed at least at the opposite ends of the respective groups of the recording elements.
It may be that at least one recording element driving signal contact is connected to each of the groups of said recording elements to supply driving signals for generating the ejection energy to said recording elements therein with the same pulse width to cause said recording elements to generate ink ejection energy.
It may be that the groups of the recording elements have a length not less than 20 mm.
According to a further aspect of the present invention, there is provided a driving method for an ink jet recording head including a substrate having a plurality of recording elements arranged in an array on a substrate, said recording elements having electric resistances with a variance not less than 4% from a resistance value of at least one of said recording elements, wherein the recording elements generate ink ejection energy to effect printing; and a plurality of measuring elements, disposed adjacent at least each of the opposite ends of the array of said recording elements, for detecting characteristic values of said recording elements, said method comprising:
a step of detecting characteristic values of the measuring elements, from which an average, a median or a reference value corresponding thereto is obtained;
a step of determining amounts of electric energy of driving signals to be supplied to the recording elements to generate the ejection energy on the basis of the average, the median or the reference value responding thereto; and
a step of supplying the driving signals having the amounts of electric energy thus determined to the recording elements.
According to an aspect of the present invention, optimum amounts of electric energy can be supplied to the recording elements, and therefore, the damage to the recording elements and/or ink ejection defect due to the shortage of the energy can be avoided.
It may be that said recording head further includes storing means for storing the average, the median or the reference value corresponding thereto, said method further comprising a step of reading the average, the median or the reference value corresponding thereto out of said storing means before said determining step.
It may be that the characteristic values are resistances of the measuring elements.
It may be that said array of the recording elements is divided into a plurality of groups of said recording elements, and said plurality of measuring elements for detecting characteristic values of said recording elements are disposed at least at the opposite ends of the respective groups of the recording elements.
It may be that at least one recording element driving signal contact is connected to each of the groups of said recording elements to supply driving signals for generating the ejection energy to said recording elements therein with the same pulse width to cause said recording elements to generate ink ejection energy.
It may be that the groups of the recording elements have a length not less than 20 mm.
It may be that the amounts of the electric energy of the driving signals to be supplied to said recording elements are capable of being controlled for respective groups.
It may be that the amounts of the electric energy of the driving signals to be supplied to said recording elements are the same within the respective groups.
According to an aspect of the present invention, the variations of the resistances of the recording elements relative to the resistance value can be made one half the conventional variations. Therefore, even if the size of the substrate is relatively large, the influence of the variations in the resistances is small, and therefore, the problems of the short service life of the recording head and/or the recording defect due to the shortage of the energy can be avoided. Simultaneously, the yield of the recording head manufacturing can be increased, and the manufacturing cost can be reduced.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.